Various methods for terrestrial transmission of digital broadcast signals are known, having modulation types like OFDM, QPSK and QAM. Examples for such broadcast signals are DVB (digital video broadcast), HDTV-T (hierarchical digital television transmission) and DAB (digital audio broadcast) signals.
At the OFDM method (Orthogonaly Frequency Division Multiplexing) the transmitted signal includes a multiplicity of modulated carriers. These carriers are separated in the receiver by means of a Fast Fourier Transformation (FFT). Before being transposed in the frequency domain, the analog signal must be sampled. For this purpose a local oscillator controls the timing in front of the FFT. Oscillator imperfections (jitter, frequency offset) can degrade the accuracy of the sampling operation and therefore introduce intercarrier interferences after the FFT. The Automatic Frequency Control processing (AFC) and the Common Phase Error Estimation processing (CPEE) are suited to give estimates of the frequency errors in order to correct the oscillator imperfections.